The Positive Energy Balance
Why would anyone willingly continue to overeat or remain sedentary if obesity is the undesirable state it certainly appears to be? Why would energy balance remain positive when there is so much time to stop the process and maybe reverse it? If a positive energy balance can be turned around by exercise and calorie restricted diets, why is it so difficult to lose weight?
This is the paradox that haunts a century of obesity research despite statements like Marian Burros of the New York Times who wrote in 2004, “Those who consume more calories than they expend in energy will gain weight. There is no getting around the laws of thermodynamics.” However, we know that the great majority of those who attempt to expend more calories than they consume don’t lose weight. Those who do, only lose a little for a short period of time. I have personally lost weight on a low-fat diet only to have it return. Fortunately, I found a low carbohydrate diet before I gained it all back! Albert Stunkard called obesity, a “chronic condition.”
In 1983, Jules Hirsch of Rockefeller University gave us two alternative hypotheses. One, obesity is the result of a “willful descent into self-gratification.” The other is “there is something biologic about obesity, some alteration of hormones, enzymes or other biochemical control systems which leads to obesity.” Hirsch believed that it was perhaps better to maintain the illusion that obesity is not an illness. It is more pleasant to believe that it is not more than an error of good judgment and that better judgments and choices will eventually lead to a better outcome.
The deposition of fat in men and women is distinctly different. Men tend to store fat above the waist and women below it. Women put on fat in puberty, at least in the breast and hips, and men lose it. Women gain fat in pregnancy and after menopause. This suggests that sex hormones are involved as much as or more than eating behavior and physical activity.
Fat tends to run in families as Hilde Bruch noted in 1957, and the characteristic shapes or body types “are as striking as facial resemblance.” Perhaps it is genetics and not the environment that accounts for a large proportion of the population today, as Jeffrey Friedman of Rockefeller University put it in 2004. If obesity does have such a significant genetic factor, equivalent to height and greater than that of almost every other condition that has been studied, then how does this figure into the equation of overeating and sedentary behavior?
The same can be said about metabolic or hormonal factors. It’s well known that infants born to diabetic mothers are heavier at birth, are relatively fatter and have a higher rate of subsequent obesity than infants of non-diabetic mothers of equal age. Couldn’t the same be true for those of us without diabetic mothers?
Some of us seem predisposed to put on weight from infancy onward. In 1940, Harvard physiologist William Sheldon said “we do not need a science to tell us that no two human beings are alike.” He described humans as either ectomorphs who are tall and lean; mesomorphs, who are broad and muscular; and, endomorphs, who are round and fat. “You can starve endomorphs and they might lose weight and appear emaciated but they will not change into mesomorphs or ectomorphs any more than a starved mastiff will change into a spaniel or a collie. “
In 1977, Oklahoma Senator Henry Bellmon captured this dilemma perfectly before the McGovern committee. “I want to make sure we don’t oversimplify. We make it sound like there is no problem for those of us who are overweight except to push back from the table sooner. But I watched Senator Robert Dole in the Senate dining room eat a double dip of ice cream, a piece of blueberry pie, meat and potatoes, yet he stays as lean as a Kansas coyote. Some of the rest of us who live on lettuce, cottage cheese and Ry-Krisp don’t do nearly as well. Is there a difference in individuals as to how they utilize fuel?”
The evidence was clear but it was difficult to reconcile with the dogma that obesity is caused by gluttony and sloth. Over the past century there have been studies that addressed how easily some of us fatten than others. In the 1960s, Endocrinologist Ethan Sims from the University of Vermont induced volunteers to overeat to considerable excess for months at a time. He used to use students, but he found it difficult to get them to gain significant weight. He used convicts at Vermont State Prison by raising their calories by 4,000 calories per day. They gained a few pounds but then their weights stabilized. He had them eat 5,000 calories per day, then seven thousand, then ten thousand while remaining sedentary.
Sims reported that there were “marked differences between individuals in ability to gain weight.” Eight subjects went two-hundred days on this regimen and two gained weight easily and six did not. One managed to gain less than ten pounds after thirty weeks of forced gluttony.
When the experiment ended, all the subjects “lost weight readily with the same alacrity“as obese patients turn to their weights after semi-starvation diets. Sims concluded that all of us are endowed with the ability to adopt our metabolism and energy expenditure in response to over and under nutrition but some of us, as with any physiological trait, do it better than others.
Claude Bouchard of the Pennington Biomedical Research Center in Louisiana overfed twenty-four groups of twenty-four young men – twelve pairs of identical twins – by a thousand calories per day, six days a week, for twelve weeks. The weight gain varied from nine to thirty pounds. In 1999, James Levine from the Mayo Clinic reported that he overfed sixteen healthy volunteers by a thousand calories per day, seven days a week, for eight weeks. The fat put on ranged from less than a pound to almost nine.
None of these experiments could explain what happened to the extra calories in those subjects who did not fatten easily and why some of these subjects fattened more than others. Bouchard found that twin pairs tended to gain similar amounts of fat and weight. “Genetic factors are involved” is all they would say.
Those involved with animal husbandry have always been implicitly aware of the genetic, constitutional component of fatness. This is why they breed livestock to be more or less fatty, just as they breed dairy cattle to increase milk production, racehorses for speed and endurance, or dogs for hunting or herding ability. It’s conceivable that these breeders have identified genetic traits that determine the will to eat in moderation and a propensity to exercise, but it strains the imagination that these are the relevant factors.
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